BrightBox routers are supplied by EE to its broadband and fibre customers. But Helme discovered vulnerabilities that exposed WPA encryption keys, passwords and users' ISP credentials.

Worse yet, flaws with the technology created a means for hackers to change a router's DNS settings in order to intercept a target's internet traffic.

Sensitive data, including Wi-Fi SSIDs and WPA2 keys, is stored in a file called cgi_status.js that can be accessed without logging into the Brightbox routers, which was made by Taiwan-based manufacturers Arcadyan.

As with many items of consumer networking equipment, the root cause of the problem stemmed from a failure to build security into the router's design. Confidential information was accessible remotely as the result of a cross-site reference forgery flaw involving the router's admin panel.

Helme, an EE customer, carried out his research because of his interest in information security. As many as 700,000 EE customers in the UK were left exposed to attack as a result of the security shortcomings of the kit they use to connect to the internet.

The researcher went public with his findings last month, two months after notifying EE about the problem. In response, EE downplayed the exploitability of the problems while acknowledging there was an issue and promising to develop a fix.

EE notified Helme that it was beginning the phased rollout of an update last week. Helme said the update fixed two out of the three most serious flaws he identified.

"EE were kind enough to flash my device with the firmware patch over the wire; they wouldn't provide the actual file to me," Helme told El Reg by email.

"It seems that the update is a two out of three. They fixed the exposure of passwords/usernames/etc and the remote management exploit, but haven't fixed the CSRF exploit. This means I can still do things like change your router's DNS servers and then intercept every packet of data that goes through it, factory reset your device, enable Wi-Fi networks etc etc. There are also several other less serious security issues that they haven't addressed that I raised with them including session fixation attacks and session hijacking attacks."

Helme destroyed his original device quite spectacularly, using a licensed shotgun, but has since bought a replacement on eBay and is continuing to research the security of the technology.

An EE spokeswoman said that the patch was developed and tested as quickly as possible.

"We started rolling out a firmware update to our customers last month, following the identification of security issues affecting the software platform that the BrightBox product is built on," said the spokeswoman. "This is a phased, remote roll out. All new BrightBox 1 routers shipped now include the new firmware."

She added that EE were aware of the CSRF bug and are working on a second patch to fix it.

Andrew Ferguson, site editor at independent analysis website thinkbroadband.com, said: “Security vulnerabilities like the one highlighted in the EE Brightbox go beyond simply stealing Wi-Fi access and can leave users at risk to phishing scams and malware installation."

"Aside from gaps in security design, there are likely millions of broadband routers in the UK that are still running on the default administrator username and password, meaning that access can be gained by simply trying three or four different username password combinations. The past has also shown that while some routers are supplied with unique wireless encryption keys - these can be guessed as the random allocation algorithm during the manufacturing process is not truly random.”

"The Brightbox is not the first consumer broadband hardware to have vulnerabilities exposed and will not be the last," he added. ®